Magnetic heads are used in disk drives to write information on to a moving magnetic media and to read the information stored thereon. Conventional magnetic heads include a write head and a read head. A write head should be capable of writing straight and sharp transitions. The write head should also be capable of writing the data on a given track without reducing the signal of adjacent or nearby tracks.
The write head may implement a longitudinal recording mode or a perpendicular recording mode for magnetically encoding data on a disk. A longitudinal write head, in accordance with the conventional art, is depicted in FIG. 1A. In longitudinal recording, a coil 105 wound around a toroid 110 generates a magnetic flux. The fringe field 115 proximate a gap in the toroid 110 causes orientation of a magnetic recording layer 120, having a horizontally orientated magnetic domain, on a disk as a function of the current through the coil 105.
A perpendicular write head, in accordance with the conventional art, is depicted in FIG. 1B. In perpendicular recording, a current flowing in the coil 155 creates a magnetic flux in a write pole 160. The magnetic flux 165 passes from the tip of the write pole 160, perpendicularly through the magnetic recording layer 170, having vertically orientated magnetic domain, and into a soft underlay 175. The bit cell recorded on the magnetic recording layer has a width representing track-width, a length representing linear density and a depth that provides the volume necessary to provide sufficient magnetization to be read by a sensor of the read head.
The areal density achievable by a write head is a product of the linear bit density and the track density. The linear bit density is the number of bits that can be written per linear inch along the track of the rotating magnetic disk. The track width density is the number of tracks that can be written per inch along a radius of the disk. The linear bit density depends upon the length of the bit along a track and the track-width density is dependent upon the width of the pole tip.
A perpendicular recording magnetic disk is thicker than a longitudinal disk and therefore provides sufficient magnetization for a bit cell having a decreased width and or length. Accordingly, the width and the length of the write probe at the tip (e.g., air bearing surface) can be reduced to increase the track-width density and/or linear bit density.
The flux field generated by the write pole is dependent upon the flare length, the flare point, the trailing edge and other structures of the write pole. Simultaneously controlling the flare point and control the track-width of the write pole, utilizing conventional methods of fabrication, such as ion milling, is problematic. Thus, reducing the width and/or length of the write pole tip may create a magnetic field adjacent to the bit but outside of the track in which the writing process is taking place, thereby corrupting the bits on adjacent tracks. Similarly, it becomes more difficult to simultaneously maintain the planarity of the trailing edge of the write pole as the width and/or length is decreased using an ion mill approach. A reduction in the quality of the trailing edge may reduce the quality of the linear transition between each bit. Accordingly, what is needed is a write pole structure characterized by a flux field having an improved field gradient to write into high coercivity media while minimizing adjacent track interference (ATI).